We have noted key differences between the cancer estimation approaches in the Global Burden of Disease (GBD) Study and the International Agency for Research on Cancer (IARC) project GLOBOCAN,1,2 which Freddie Bray and colleagues have taken issue with. With regard to data, the GBD uses all the data reported by the IARC plus cause of death data from vital registration systems and other sources, along with cancer registries not collated by the IARC. However, the most important distinction concerns estimation methods.